Hydraulic remote control apparatus



May 19, 1964 J. ROLLITT.

HYDRAULIC REMOTE CONTROL APPARATUS S-Sheets-Sheet 1 Filed Sept. 14, 1960 INVENTOR:

JO HN ROLL HT 90 g as i v' y .1964 J. ROLLITT 3,133,419

HYDRAULIC REMOTE CONTROL APPARATUS Filed Sept. 14. 1960 5 Sheets-Sheet 2 INVENTOR:

I OHH KOLLHT BY May 19, 1964 J. ROLLITT HYDRAULIC REMOTE CONTROL APPARATUS 5 Sheets-Sheet 4 Filed Sept. 14. 1960 INVENTOR: Jon ROI-LITT- May 19, 1964 .1. ROLLITT 3,133,419

HYDRAULIC REMOTE CONTROL APPARATUS Filed Sept. 14. 1960 5 Sheets-Sheet 5 INVENTOR:

JOHN ROLUTT M M, M W

United States Patent 3,133,419 HYDRAULIC REMQTE ONTROL APPARATUS John Roilitt, Copmanthorpe, York, England, assignor to Armstrong Patents Co. Limited, London, Engiand Filed Sept. 14, 1960, Ser. No. 56,030 7 Claims. (Cl. 60-545) This invention concerns a hydraulic remote control apparatus, and relates more particularly to a hydraulic looking valve assembly and to a control unit for controlling the supply of hydraulic medium under pressure to and the exhaust of hydraulic medium from a hydraulically operated, double-acting load displacing member or members.

According to the present invention, in a hydraulic locking valve assembly for use in a hydraulic system of the type wherein a hydraulically operated, double-acting loaddisplacing member is actuated by hydraulic medium under pressure fed from a pressure source, when said hydraulic medium is directed to open one of a pair of valves arranged at spaced positions in a bore of the assembly to control communication of said assembly with said loaddisplacing member, then it simultaneously displaces a piston arranged in said bore between said Valves, and said piston displacement is employed to open the other valve and permit the flow of returning hydraulic medium from said load-displacing member.

A preferred form of the locking valve assembly accord ing to the present invention comprises a body formed with a first pair of hydraulic connections adapted to receive hydraulic medium supply and return pipes, a second pair of hydraulic connections each adapted to receive a pipe for conveying hydraulic medium between said body and said load-displacing member, the connections of said second pair being arranged to communicate one with either end region of a bore formed in said body, a valve seat arranged at either end region of said bore, a valve member resiliently urged against said seat to normally isolate the adjoining hydraulic connection from the remainder of said bore, a freely displaceable piston situated in said bore intermediate said valve seats and isolating said valve seats from one another, the hydraulic connections said first pair of connections each communicating with said bore between one end of said piston and the adjacent valve seat.

The hydraulic locking valve assembly may conveniently be incorporated in a control unit for controlling the operation of the load displacing member by the pressure source, such control unit further having a changeover valve in said body and arranged selectively to place the first-mentioned pair of hydraulic connections of the locking valve assembly in communication with the two regions of the said bore separated by the displaceable piston. In

this way, the pressure source may be selectively connected to either one of the second-mentioned pair of hydraulic connections in order to actuate the load-displacing member in a desired direction, the other one of said second pair of connections then serving for. the return flow of hydraulic medium from the load-displacing member.

The change-over valve may conveniently comprise a plunger slidable in a further bore formed in the unit body and to which the hydraulic medium from the source thereof is delivered, the plunger having a number of axially spaced, circumferential recesses or grooves adapted to cooperate with enlarged diameter regions of said further bore in directing the hydraulic medium to the selected hydraulic connection.

The source of hydraulic medium under pressure may be, for example, a pressure accumulator or a pump; and where a pump is used, such pump is preferably doubleacting, and may comprise a pair of pistons arranged either 3,133,419 atented May 19, 1964 in opposed, end-to-end or in parallel, side-by-side relationship, and operable from a semi-rotary spindle journalled in the pump body. If desired, the hydraulic control unit and the source of hydraulic medium under pressure may be combined in a single body, or alternatively, a single source of hydraulic medium may supply a plurality of control units arranged in a single assembly positioned at some convenient location and each adapted to control one of a corresponding number of remote load-dis placing members.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a vertical sectional elevation of a hydraulic control unit embodying a built-in or integral pump;

FIG. 2 is a detail, to an enlarged scale, of a pump piston;

FIG. 3 is a section taken on the line III-III of FIG. 1;

FIG. 4 is a section taken on the line IV-IV of FIG. 1, with parts omitted for clarity.

FIG. 5 is a section taken on the line VV of FIG. 1;

FIG. 6 is a sectional detail, to an enlarged scale, of a part of a pressure responsive valve means;

FIG. 7 is a schematic diagram showing the arrangement of the unit in a hydraulic remote control system;

FIG. 8 is a section taken on a central plane through a hydraulic locking valve constructed according to the invention; and

FIG. 9 isa horizontal, sectional elevation of another hydraulic control unit embodying the invention.

Throughout the. drawings, similar reference numerals are employed wherever possible to denote similar parts.

The hydraulic pumping and control unit shown in FIGS. 1 to 7 of the drawings has a body 1% which,

of compression springs 22 arranged in said cylinders, and

the spindle 20 is provided, externally of the body 10, with an arm 24 (FIG. 7) reciprocable between limits determined by means of stops 26 against which the con necting rods 16 can bear, and hence on oscillation of the arm 24, the pistons 14 are reciprocated between corresponding limits in their cylinders.

One of the pistons 14 is shown in more detail in FIG. 2 and will be seen to include a pair of inclined radial bores 28 opening at its outermost end, and an axial bore 30 into which the bores 28 lead and which is counterbored to receive a valve seat 32 against which is urged a Valve ball'34 by means of a spring 36 retained in the counterbore by a bush 38. The cylinders 12, at their free ends, open into a reservoir 40 formed within the .body 10, and thus, when the pistons are reciprocated, hy-

draulic medium is drawn into the cylinders 12 through the piston bores 28 and 30 and past the valve ball 34. At their ends remote from the reservoir 40, the cylinders 12,

as shown in FIG. 3, each open into a delivery conduit 42 formed in the body 10, and the delivery conduits 42 each lead by way of a delivery valve 44 into a chamber 46 3 to receive pipes 52 whereby, as shown in FIG. 7, the pumping and control unit may be connected to an appropriate hydraulically operated load-displacing member generally designated 54. By way of example, the load-displacing member 54 is shown as comprising a pair of pistons 56 displaceable in cylinders 58 formed in the body of the member 54, and coupled by connecting rods 60 to a crank plate 62 fixedly secured on a shaft 64 journalled in said body. The shaft 64, externally of said body, carries an arm 66 adapted to displace a load diagrammatically indicated by the reference character W, and it will be readily appreciated that angular movement of the arm 66 may be employed to offset window and door opening and closing movements, and many other load-displacing movements. Other examples of load-displacing members are those wherein the pistons 56 are arranged in opposed, end-to-end relationship instead of the parallel, side-byside relationship shown, and wherein said displacing mem her is of a telescopically extensible and retractible nature. It will be appreciated that one pump may supply more than one load-displacing member, by connecting a plurality of load-displacing members either in series or in parallel for simultaneous or sequential operation of all such members. If, in the particular example shown in FIG. 7, the lower cylinder is supplied with hydraulic medium, then the load W will be lifted as the shaft 64 is rotated in an anti-clockwise direction, and conversely, the load W will be lowered if hydraulic medium is supplied to the upper cylinder 58. To achieve this, it is necessary to connect the cylinder 58 concerned to the hydraulic medium delivered to the chamber 46, via the appropriate one of the connections 50. As shown in FIG. 7 the lever 83 is set to supply hydraulic medium to the upper cylinder 58. For supplying hydraulic medium to the lower cylinder 58, the lever 88 is set as shown in FIG. 4.

FIG. 4 shows a change-over valve for selectively conmeeting the chamber 46 to either one of the outlet connections 50. The body is formed with a bore 68 having diametrically enlarged regions 70, 72 and 74, and within the bore 68 is slidingly engaged a plunger 76 having its external surface recessed at 80 and 82 to cooperate with the enlarged regions of the bore 68. One end of the plunger 76 projects from the bore 68, and is formed with a horizontal slot 84 wherein engages a peg 86 of a lever 88 pivotally secured at 90 to the body 10. The enlarged diameter region 72 of the bore 68 communicates by way of a passage 92 with the chamber 46 and thus, depending on the setting of the lever 88 and therefore of the plunger 76, hydraulic medium delivered from the chamber 46 to the said region 72 passes along the recess 30 to either the enlarged region 70 or the enlarged region 74 of the bore 68. From the said regions 70, 74, the body 10 is formed with passages 94 and 9s respectively, leading to a further bore 98, at opposite end regions of which the connection 59 are arranged, the region of the bore 98 between the passages S 4 and 96 being occupied by a floating piston 1&0 fitted at each end with a restoring spring 101. Thus, depending on the afore mentioned setting of the lever 86, hydraulic medium is delivered to one or other of the said connections 50. I

Reverting to the hydraulic system shown in FIG. 7, it is desirable that, once the load W has been displaced into a desired position, it should thereafter be held locked in that position until such time as it is required to be released. The communication between each of the passages 94 and 96 and their respective connections 50 is accordingly provided with a non-return valve comprising a valve ball 162 (FIG. 6) resiliently urged by means of a spring 104 on to a seat 106. The valve ball'1ti2, spring 104 and seat 1% are retained within a hollow plug member 1G8, sealing the end of the bore 98, by means of a retaining nut 111 which is axially bored at 112, has an interval seat 113, and counterbored at 114 to receive a push rod 116 having a radial annular flange 118 intermediate its ends. The plug member is provided with radial bores 120 opening into an annular recess 122 to allow the passage of hydraulic medium issuing past the valve ball 102 into the connection 50.

In the operation of the unit described above, if it is desired to lift the load W, then the lever 38 is set to cause the recess 89 of the plunger 76 of the change-over valve to direct hydraulic medium from the chamber 46, the passage 92 and enlarged diameter region 72 of bore 68 to the connection 50 communicating with the lower pipe 52. On reciprocation of the arm 24, hydraulic medium is then pumped from the reservoir to the lower one of the cylinders 58 in the load-displacing unit 54 to displace the piston 56 therein and hence the crank plate 62, spindle 64 and arm 66, and after the displacement of hydraulic medium resulting from each pumping stroke of the handle 24, the valve ball 102 associated with the connection 563 concerned closes on to its seat to act as a hydraulic locking valve which prevents the return, due to the downward weight exerted by the load, of hydraulic medium back through the same pipe 52 to the pumping and control unit. Since the resulting anti-clockwise movement of the crank plate 62 displaces the upper piston 56 in a direction opposite to that of the lower piston 55, provision must be made to permit the return of hydraulic medium from the upper cylinder 58 to the reservoir 4%. This is accomplished in that, when the plunger 76 is set to direct hydraulic medium, for example, through the passage 96 to the left-hand end of the bore 98 (as viewed in FIG. 4), the piston is urged to the right by the pressure of said hydraulic medium, and, after firstly compressing the restoring spring 1131 at the right-hand end of the piston, causes the right-hand push rod 116 to unseat the adjacent valve ball 102, thus opening a path for hydraulic fluid to return via the righthand connection 50, the associated plug member 198, the bore 98, passage 94 and a further passage 124 formed in the body 169 between the bore 98 and the reservoir 40. Conversely, when the plunger 76 is set to direct outwardly flowing hydraulic medium through the passage 94 to the right-hand end of bore 98 (as shown in FIG. 7), the path for return flow of hydraulic medium is through the left-hand connection St), the passage 96 (valve ball 102 having been lifted by piston 1%), the enlarged diameter portion 74 of the bore 63, the recess 82 of plunger 76 and then through an axial bore 126 of the plunger to the passage 124 and the reservoir 40. It will be noted, however, that even when the appropriate valve ball 102 has been unseated by the piston to open the return flow path as described, no flow of hydraulic medium can take place along that path until the pressure of hydraulic medium on the other valve ball 102 is sufiicient to unseat that valve ball against the pressure of the hydraulic medium in the pipe 52 due to the reaction of the weight W and tending to hold the said other valve ball closed. Thus, only when the outward flow path for hydraulic medium is open and an adequate load-displacing hydraulic pressure has been established can the pistons 56 move, and only then can corresponding return flow take place. 'In this way, the load W is, in effect, hydraulically locked in any displaced position which is imparted to it, and, in the particular arrangement shown in FIG. 7, it follows that the load W can, so to speak, be pumped down from a raised position, as well as pumped up from a lowered positionj Moreover, in order to ensure that the load W remains accurately in any position to which it has been moved by the application of hydraulic pressure, it will be noted that the annular flange 113 of the push rod 116 co-operates with the counterbore 114 to constitute a flow restriction for hydraulic medium attempting, when the hydraulic pressure is removed, to return past the valve 192 concerned. In the absence of a flow restriction, the pressure differential between the loaded and the unloaded sides of the valve ball 192, and due to the reaction of the load W, can result during fluid flow in the creation between the valve ball 102 and its seat, of

a pressure sufficiently high to momentarily hold the ball 102 off its seat despite the provision of the valve spring 104. The flow restriction afforded by the annular flange 118, however, largely prevents the creation of such a pressure differential, and allows the spring 104 to act efiiciently in restoring the valve ball 102 promptly to its seat when the applied, load-displacing hydraulic pressure is removed.

Although the unit described above has been shown as being hand-operated by means of the arm 24, power operation may be achieved by connecting the spindle 20 through any suitable cam or equivalent mechanism to a prime mover such as an electric motor.

As shown in FIG. 8, the hydraulic locking valve assembly proposed by the invention may be used by itself for some purposes. FIG. 8 shows the hydraulic locking valves contained in a body 11 having inlet connections 49 adapted for communication with a source of hydraulic medium under pressure, and outlet connections 50 for communication with one or more loaddisplacing members. The inlet connections 49 open into the passages 94 and 96, by selection of which the hydraulic medium is directed to the required side of the piston 100, and the outlet connections 50 open into the recesses 122 and the radial bores 120 (not shown in FIG. 8) of the plug members 108. As before, the plug members 108 house the valve ball locking members 102 of the preceding embodiment, and the construction and operation of the assembly shown in FIG. 8 is in all other respects identical with the corresponding description of that preceding embodiment.

One particularly useful application of the assembly of FIG. 8 is in hydraulic systems of the type shown in FIG. 7, wherein the pipe lines 52 are either long and/or of a plastic or synthetic resin material. Such pipes are liable to flex under the hydraulic'pressures employed, and

thus can permit the load W to flex even when the valve ball 102 of a hydraulic locking valve situated remote from the load-displacing member 54, e.g. in the body of FIG. 7, is securely seated. The provision of a locking valve assembly according to FIG. 8, close to the member 54 of FIG. 7, has been found satisfactorily to eliminate this problem, since the length of pipe line 52 between such assembly and the load W is then negligible.

FIG. 9 shows how the change-over valve and the hydraulic locking valve may advantageously, for many purposes, be arrangedas a combined unit contained in a body 11a. The body 11a is provided with the hydraulic connections 50, and with a hydraulic medium inlet 91 and outlet 123 corresponding respectively to the passages 92 and 124 of the embodiment of FIGS. 1 to 7. The inlet 91 and outlet 123 are adapted for connection in any convenient manner (not shown) to a source of hydraulic medium under pressure, the inlet 91 admitting hydraulic medium to the recess 72, and the outlet 123 accepting hydraulic medium from. the recess '70, either directly or by way of the plunger bore 126, for return to the low pressure side of the source. In all other respects, the construction and operation of the control unit shown in FIG. 8 is identical with that already described with particular reference to FIGS. 4 to 6. Such a unit may thus be connected to a constant source of hydraulic medium under pressure, such as a pressure accumulator and actuation of a double-acting load-disp1acing member (for example, the member 54 of FIG. 7) in ,either direction is then accomplished by simple operation of the lever 88 of the change-over valve.

' It will be appreciated that a number of the control units of FIG. 9 may be juxtaposed to constitute a single assembly, all conveniently capable of being connected to the same pressure source, but each controlling the opera- For this purpose,the body 11a is bored at 150 (FIG. 9)

G to receive bolts 152 or other suitable fastening means for securing the several units together in the one assembly.

It will also be appreciated that the hydraulic control unit of FIG. 9 may be fitted with a pump similar to that of the embodiment of FIGS. 1 to 7.

Although the reservoir 40 is sufiicient to store adequate hydraulic medium for most purposes, the reservoir capacity may readily be increased if desired, as shown in FIG. 1, by interposing an additional body section 10a between the body 10 and a cover 10 therefore.

I claim:

1. A hydraulic locking valve assembly for use in a hydraulic system of the type wherein a hydraulically operated, double-acting load-displacing member is actuated by hydraulic medium under pressure fed from a pressure source, said assembly comprising a body formed with a first pair of hydraulic connections adapted to receive hydraulic medium supply and return pipes from said pressure source, a second pair of hydraulic connections each adapted to receive a pipe for conveying hydraulic medium between said body and said load-displacing member, said second pair of connections communicating one with either end region of a bore formed in said body, a valve seat arranged at each said end region, a valve member resiliently urged against each seat for isolating the adjoining hydraulic connection from the remainder of said bore, and a freely displaceable piston disposed in said bore intermediate said valve seats and isolating said valve seats from one another, said first pair of hydraulic connections each communicating with said bore between one end of said piston and the adjacent valve seat, two push rods displaceably mounted one adjacent to each valve member for unseating said valve member responsive to displacement of said piston when the other valve member is unseated by hydraulic pressure, and two guide members one mounted adjacent to each valve seat and in each of which one of said push rods is displaceably mounted, said push rod and associated guide member cooperating to define a flow restriction serving to limit the pressure differential created between opposite sides of the valve seat when hydraulic medium flows therethrough, said flow restriction increasing as the push rod moves away from the valve member.

2. A hydraulic locking valve assembly comprising a body, said body having a bore located therein, two valve seats arranged one at each end of said bore, two valve members resiliently urged one against each seat, a piston displaceable in said bore between said valve seats, two hydraulic connections communicating with said bore between said valve seats and on opposite sides of said piston, two further hydraulic connections each of which communicates with said bore adjacent to one of said valve seats and on the opposite side of said seat from said first-mentioned hydraulic connections, two push rods displaceably mounted one adjacent to each valve member for unseating said valve member responsive to displacement of said piston when the other valve member is unseated by hydraulic pressure, and two guide members one mounted adjacent to each valve seat and in each of which one of said push rods is displaceably mounted, said push rod and its associated guide member cooperating to define a flow restriction serving to limit the pressure difierential created between opposite sides of the valve seat when hydraulic medium fiOWs therethrough,

said flow restriction increasing as the push rod moves away from the valve member.

3. A hydraulic control unit comprising a body, said body having a first bore and a second bore located therein, two passages in said body, each connecting said first bore with said second bore, two valve seats arranged one at each end of said first bore such that said passages communicate with the space between said valve seats, two valve members resiliently urged one against each seat, a piston displaceable in said first bore between said valve seats, said passages communicating with the first bore on opposite sides of said piston, two hydraulic connections each of which communicates with said first bore adjacent to one of said valve seats and on the opposite side of said seat from said passages, two push rods displaceably mounted one adjacent to each valve member for unscating said valve member responsive to displacement of said piston when the other valve member is unseated by hydraulic pressure, two guide members one mounted adjacent to each valve seat in each of which one of said push rods is displaceably mounted, said push rod and its associated guide member cooperating to define a flow restriction serving to limit the pressure differential created between opposite sides of the valve seat when hydraulic medium flows therethrough, said flow restriction increasing as the push rod moves away from the valve member, a plunger slidable in said second bore, said plunger having axially spaced, circumferential recesses, and said second bore having enlarged diameter regions, and two further hydraulic connections communicating with said second bore, the recesses on the plunger and the enlarged diameter regions of the second bore being arranged to cooperate on positioning of the plunger to place said further hydraulic connections selectively in communication with said passages connecting the first and second bores.

4. A hydraulic control unit comprising a body, said body having a first bore and a second bore located therein, two passages in said body, each connecting said first bore with said second bore, two valve seats arranged one at each end or" said first bore such that said passages communicate with the space between said valve seats, two valve members resiliently urged one against each seat, a piston displaceable in said first bore between said valve seats, said passages communicating with the first bore on opposite sides of said piston, two hydraulic connections each of which communicates with said first bore adjacent to one of said valve seats and on the opposite side of said seat from said passages, two push rods displaceably mounted one adjacent to each valve member for unseating said valve member responsive to displacement of said piston when the other valve member is unseated by bydraulic medium under pressure through one of said passages, two guide members one mounted adjacent to each valve seat and in each of one of said push rods is displaceably mounted, said push rod and its associated guide member cooperating to define a fiow restriction serving to limit the pressure differential created between opposite sides of the valve seat when hydraulic medium flows therethrough, said how restriction increasing as the push rod moves away from the valve member, a plunger slidable in said second bore, said plunger having axially spaced, circumferential recesses, and said second bore having enlarged diameter regions, and two further hydraulic connections communicating with said bore, the recesses on the plunger and the enlarged diameter regions of the second bore being arranged to cooperate on positioning of the plunger to place said further hydraulic connections selectively in communication with said passages connecting the first and second bores.

5. A hydraulic control unit comprising a body in which are located a first bore, a second bore and a hollow pump housing, the hollow interior of said housing constituting a reservoir for hydraulic medium, two passages in said body, each connecting said first bore with said second bore, two valve seats arranged one at each end of said first bore such that said passages communicate with the space between said valve seats, two valve members resiliently urged one against each seat, a piston displaceable in said first bore between said valve seats, said passages communicating with the first bore on opposite sides of said piston, two hydraulic connections each of which communicates with said first bore adjacent to one of said valve seats and on the opposite side of said seat from said passages, two push rods displaceably mounted one adjacent to each valve member for unseating said valve member responsive to displacement of said piston when the other valve member is unseated by hydraulic pressure, two guide members one mounted adjacent to each valve seat and in each of which one of said push rods is displaceably mounted, said push rod and its associated guide member cooperating to define a flow restriction serving to limit the pressure differential created between opposite sides of the valve seat when hydraulic medium iiows therethrough, said flow restriction increasing as the push rod moves away from the valve member, a manually operable plunger slidable in said second bore, said plunger having axially spaced circumferential recesses and said second bore having enlarged diameter regions, and two further hydraulic connections communicating with said second bore, the recesses on the plunger and the enlarged diameter regions of the second bore being arranged to cooperate on positioning of the plunger to place said further hydraulic connections selectively in communication with said passages connecting the first and second bores, a pair of hydraulic cylinders formed in parallel side-by-side relation in said housing, a pump piston in each cylinder and passage means including an inlet valve in each pump piston, said passage means communicating with said reservoir, a semi-rotary spindle journalled in said housing, means connecting said pump pistons and said spindle for reciprocation of said pistons within said cylinders responsive to turning movements of said spindle relative to said housing, delivery valve means in said housing connecting the ends of the cylinders remote from the spindle to one of said further hydraulic connections communicating with said second bore and the other of said further hydraulic connections communicating with the reservoir at the end of said connection remote from the second bore.

6. A hydraulic remote control system comprising a double-acting hydraulic pump, a double acting load-displacing member arranged to be actuated by hydraulic medium under pressure fed from said pump, a hydraulic locking valve assembly, supply and return pipes between said pump and said locking valve assembly and supply and return pipes between said locking valve assembly and said load-displacing member, said hydraulic locking valve assembly comprising a body, said body having a first bore and a second bore located therein, two passages in said body, each connecting said first bore with said second bore, two valve seats arranged one at each end of said first bore such that said passages communicate with the space between said valve seats, two valve members resiliently urged one against each seat, a piston displaceable in said first bore between said valve seats, said passages communicating with the first bore on opposite sides of said piston, two hydraulic connections each of which communicates with said first bore adjacent to one of said valve seats and on the opposite side of said seat from said passages, two push rods displaceably mounted one adjacent to each valve member for unseating said valve member responsive to displacement of said piston when the other valve member is unseated by hydraulic pressure, two guide members one mounted adjacent to each valve seat and in each of which one of said push rods is displaceably mounted, said push rod and its associated guide member cooperating to define a flow restriction serving to limit the pressure diiierential created between opposite sides of the valve seat when hydraulic medium flows therethrough, said fiow restriction increasing as the push rod moves away from the valve member, a plunger slidable in said second bore, said plunger having axially spaced, circumferential recesses, and said second bore having enlarged diameter regions, and two further hydraulic connections communicating with said bore, the recesses on the plunger and the enlarged diameter regions of the second bore being arranged to cooperate on positioning of the plunger to place said further hydraulic connections selectively in communication with said passages connecting the first and second bores.

7. A hydraulic remote control system comprising a double-acting hydraulic pump, a double acting load-dismedium under pressure fed from said pump, a hydraulic locking valve assembly, supply and return pipes between said pump and said locking valve assembly and supply and return pipes between said locking valve assembly and said load-displacing member, said hydraulic locking valve assembly comprising a body, said body having a first bore and a second bore located therein, two passages in said body, each connecting said first bore with said second bore, two valve seats arranged one at each end of said first bore such that said passages communicate with the space between said valve seats, two valve members resiliently urged one against each seat, a piston displaceable in said first bore between said valve seats, said passages communicating with the first bore on opposite sides of said piston, two hydraulic connections each of which communicates with said first bore adjacent to one of said valve seats and on the opposite side of said seat from said passages, two push rods displaceably mounted one adjacent to each valve member for unseating said valve member responsive to displacement of said piston when the other valve member is unseated by hydraulic pressure, two guide members one mounted adjacent to each valve seat and in each of which one of said push rods is displaceably mounted, said push rod having a flange which cooperates with a counterbore to define a flow restriction serving to limit the pressure differential created between opposite sides of the valve seat when hydraulic medium flows therethrough, said flow restriction increasing as said flange seats itself upon an internal seat, a plunger slidable in said second bore, said plunger having axially spaced, circumferential recesses, and said second bore having enlarged diameter regions, and two further hydraulic connections communicating with said bore, the recesses on the plunger and the enlarged diameter regions of the second bore being arranged to cooperate on positioning of the plunger to place said further hydraulic connections selectively in communication with said passages connecting the first and second bores.

References Cited in the file of this patent UNITED STATES PATENTS 2,247,302 Levy June 24, 1941 2,359,949 Van der Werff Oct. 10, 1944 2,368,659 Heineck Feb. 6, 1945 2,397,270 Kelly Mar. 26, 1946 2,410,978 Kelly NOV. 12, 1946 2,924,943 Dickinson Feb. 16, 1960 FOREIGN PATENTS 745,600 Great Britain Feb. 29, 1956 

1. A HYDRAULIC LOCKING VALVE ASSEMBLY FOR USE IN A HYDRAULIC SYSTEM OF THE TYPE WHEREIN A HYDRAULICALLY OPERATED, DOUBLE-ACTING LOAD-DISPLACING MEMBER IS ACTUATED BY HYDRAULIC MEDIUM UNDER PRESSURE FED FROM A PRESSURE SOURCE, SAID ASSEMBLY COMPRISING A BODY FORMED WITH A FIRST PAIR OF HYDRAULIC CONNECTIONS ADAPTED TO RECEIVE HYDRAULIC MEDIUM SUPPLY AND RETURN PIPES FROM SAID PRESSURE SOURCE, A SECOND PAIR OF HYDRAULIC CONNECTIONS EACH ADAPTED TO RECEIVE A PIPE FOR CONVEYING HYDRAULIC MEDIUM BETWEEN SAID BODY AND SAID LOAD-DISPLACING MEMBER, SAID SECOND PAIR OF CONNECTIONS COMMUNICATING ONE WITH EITHER END REGION OF A BORE FORMED IN SAID BODY, A VALVE SEAT ARRANGED AT EACH SAID END REGION, A VALVE MEMBER RESILIENTLY URGED AGAINST EACH SEAT FOR ISOLATING THE ADJOINING HYDRAULIC CONNECTION FROM THE REMAINDER OF SAID BORE, AND A FREELY DISPLACEABLE PISTON DISPOSED IN SAID BORE INTERMEDIATE SAID VALVE SEATS AND ISOLATING SAID VALVE SEATS FROM ONE ANOTHER, SAID FIRST PAIR OF HYDRAULIC CONNECTIONS EACH COMMUNICATING WITH SAID BORE BETWEEN ONE END OF SAID PISTON AND THE ADJACENT VALVE SEAT, TWO PUSH RODS DISPLACEABLY MOUNTED ONE ADJACENT TO EACH VALVE MEMBER FOR UNSEATING SAID VALVE MEMBER RESPONSIVE TO DISPLACEMENT OF SAID PISTON WHEN THE OTHER VALVE MEMBER IS UNSEATED BY HYDRAULIC PRESSURE, AND TWO GUIDE MEMBERS ONE MOUNTED ADJACENT TO EACH VALVE SEAT AND IN EACH OF WHICH ONE OF SAID PUSH RODS IS DISPLACEABLY MOUNTED, SAID PUSH ROD AND ASSOCIATED GUIDE MEMBER COOPERATING TO DEFINE A FLOW RESTRICTION SERVING TO LIMIT THE PRESSURE DIFFERENTIAL CREATED BETWEEN OPPOSITE SIDES OF THE VALVE SEAT WHEN HYDRAULIC MEDIUM FLOWS THERETHROUGH, SAID FLOW RESTRICTION INCREASING AS THE PUSH ROD MOVES AWAY FROM THE VALVE MEMBER. 